library(maptools)
## Loading required package: sp
## Checking rgeos availability: TRUE
library(raster)
srtm <- getData("SRTM", lon=-15.59972, lat=27.965)
library(rgdal)
library(rasterVis)
library(rgl)
library(htmlwidgets)
options(rgl.printRglwidget = TRUE)

open3d()
## wgl 
##   1
plot3D(srtm)
open3d()
## wgl 
##   2
plot3D(srtm)
rglscene <- scene3d()
# render the saved rgl scene as widget in the markdown page
rglwidget(rglscene,webGLoptions = list(preserveDrawingBuffer = FALSE))
rgl.close()